5.—(1) The scheme shall specify a proportion (not exceeding one half) as being the proportion of the whole proceeds of any lottery under the scheme which may be appropriated for the provision of prizes in that lottery; and shall require that the proportion so specified shall not be exceeded except in the special circumstances mentioned in sub-paragraph (2) below.
(2) The special circumstances referred to above are that—
(a)the proceeds of the lottery fall short of the sum reasonably estimated; and
(b)the appropriation is made in order to fulfil an unconditional undertaking as to prizes given in connection with the sale of the relevant tickets or chances; and
(c)the total amount appropriated in respect of prizes does not exceed the amount which could have been appropriated out of the proceeds of the lottery if the proceeds had amounted to the sum reasonably estimated.